Metabolism-Driven High-Throughput Cancer Identification with GLUT5-Specific Molecular Probes

Sugar functionalized coumarin motifs: Synthesis and applications

Sugars are vital biomolecules widely found in nature, playing an indispensable role in a plethora of biological processes. Similarly, coumarins are heterocycles with an effective pharmacophore skeleton, making them crucial in drug design and development. Coupling carbohydrate moieties to the small biologically active molecules creates a vast library of glycoconjugates with impressive structural diversity. The potential of coumarin glycosides is being extensively explored due to their broad spectrum of applications, including antibacterial, anticancer, and anticoagulant properties, etc. This review highlights various chemical methodologies for synthesizing diverse coumarin glycohybrids with distinct linkages and explores their immense biological potential, making a significant contribution to the field of organic synthesis.

Glycoconjugate coumarins exploiting metabolism-enhanced fluorescence and preferential uptake: New optical tools for tumor cell staining

The possibility to visually discriminate cells based on their metabolism and capability to uptake exogenous molecules is an important topic with exciting fallback on translational and precision medicine. To this end, probes that combine several complementary features are necessary. The ideal probe is selectively uptaken and activated in tumor cells compared with control ones and is not fluorescent in the extracellular medium. Fluorogenic compounds that combine enzyme-activated pH sensitivity and good cell uptake can be an ideal solution, provided that the sensed enzymes are dysregulated in tumor cells. Here, we present synthesis and in vitro evaluation of a new class of glyco-coumarin based probes that merge all these features. These probes show uptake ratio in tumor vs. control cells up to 3:1, with a cell to background ratio upon administration of the probe up to 5:1. These features make this new family of fluorogenic targeted probes a promising tool in life science.

GLUT5-overexpression-related tumorigenic implications

Glucose transporter 5 (GLUT5) overexpression has gained increasing attention due to its profound implications for tumorigenesis. This manuscript provides a comprehensive overview of the key findings and implications associated with GLUT5 overexpression in cancer. GLUT5 has been found to be upregulated in various cancer types, leading to alterations in fructose metabolism and enhanced glycolysis, even in the presence of oxygen, a hallmark of cancer cells. This metabolic shift provides cancer cells with an alternative energy source and contributes to their uncontrolled growth and survival. Beyond its metabolic roles, recent research has unveiled additional aspects of GLUT5 in cancer biology. GLUT5 overexpression appears to play a critical role in immune evasion mechanisms, which further worsens tumor progression and complicates therapeutic interventions. This dual role of GLUT5 in both metabolic reprogramming and immune modulation highlights its significance as a potential diagnostic marker and therapeutic target. Understanding the molecular mechanisms driving GLUT5 overexpression is crucial for developing targeted therapeutic strategies that can disrupt the unique vulnerabilities of GLUT5-overexpressing cancer cells. This review emphasizes the complexities surrounding GLUT5's involvement in cancer and underscores the pressing need for continued research to unlock its potential as a diagnostic biomarker and therapeutic target, ultimately improving cancer management and patient outcomes.

Recent progress in the synthesis of natural product inspired bioactive glycohybrids

Carbohydrates are a basic structural component that are indispensable to all cellular processes. In addition to being employed as chiral starting materials in the synthesis of a variety of natural products, carbohydrates are recognized as naturally occurring molecules having an enormous variety of functional, stereochemical, and structural properties. The understanding and biological roles of carbohydrate derived molecules can be greatly improved by selectively synthesizing functional carbohydrates through incorporating them with privileged scaffolds. For a deeper understanding of their roles and the development of functional materials based on sugar, it is crucial to develop new techniques for efficiently synthesizing, functionalizing, and modifying carbohydrates. Glycohybrids have a wide range of structural and functional characteristics along with protein-carbohydrate interactions that are crucial to mammalian biology and a number of disease states. This review, consisting the literature from January 2017 to July 2023 and provide an overview of recent developments in the chemical synthesis of glycohybrids based on natural product scaffolds of coumarin, quinolone, naphthalene diimide, indole, isatin, naphthoquinone, imidazole and pyrimidine. The biological activity of active glycohybrids are discussed in this review.

GLUT5: structure, functions, diseases and potential applications

Glucose transporter 5 (GLUT5) is a membrane transporter that specifically transports fructose and plays a key role in dietary fructose uptake and metabolism. In recent years, a high fructose diet has occupied an important position in the daily intake of human beings, resulting in a significant increase in the incidence of obesity and metabolic diseases worldwide. Over the past few decades, GLUT5 has been well understood to play a significant role in the pathogenesis of human digestive diseases. Recently, the role of GLUT5 in human cancer has received widespread attention, and a large number of studies have focused on exploring the effects of changes in GLUT5 expression levels on cancer cell survival, metabolism and metastasis. However, due to various difficulties and shortcomings, the molecular structure and mechanism of GLUT5 have not been fully elucidated, which to some extent prevents us from revealing the relationship between GLUT5 expression and cell carcinogenesis at the protein molecular level. In this review, we summarize the current understanding of the structure and function of mammalian GLUT5 and its relationship to intestinal diseases and cancer and suggest that GLUT5 may be an important target for cancer therapy.

Turn-on Rhodamine Glycoconjugates Enable Real-Time GLUT Activity Monitoring in Live Cells and In Vivo

The direct relationship between facilitative glucose transporters (GLUTs) and metabolic diseases opens new avenues for sensing metabolic deregulations and drives the development of molecular probes for GLUT-targeted detection of metabolic diseases. Radiotracer-based molecular imaging probes have been effectively utilized in reporting alterations in sugar uptake as an indication of metabolic deregulations, cancer development, or inflammation. Progress in developing fluorophore-based tools facilitated GLUT-specific analyses using more accessible fluorescence-based instrumentation. However, restrictions on the emission range of fluorophores and the requirement for substantial post-treatments to reduce background fluorescence have brought to light the critical directions for improvement of the technology for broader use in screening applications. Here we present turn-on GLUT activity reporters activated upon cells' internalization. We demonstrate a specific delivery of a sizable rhodamine B fluorophore through GLUT5 and showcase a stringent requirement in conjugate structure for maintaining a GLUT-specific uptake. With the turn-on GLUT probes, we demonstrate the feasibility of high-throughput fluorescence microscopy and flow cytometry-based GLUT activity screening in live cells and the probes' applicability for assessing sugar uptake alterations in vivo.

Recent advances in synthesis of sugar and nucleoside coumarin conjugates and their biological impact

Naturally occurring coumarin and sugar molecules have a diverse range of applications along with superior biocompatibility. Coumarin, a member of the benzopyrone family, exhibits a wide spectrum of medicinal properties, such as anti-coagulant, anti-bacterial, anti-tumor, anti-oxidant, anti-cancer, anti-inflammatory and anti-viral activities. The sugar moiety functions as the central scaffold for the synthesis of complex molecules, attributing to their excellent biocompatibility, well-defined stereochemistry, benign nature and outstanding aqueous solubility. When the coumarin moiety is conjugated with the sugar or nucleoside molecule, the resulting conjugates exhibit significant biological properties. Due to the remarkable growth of such bioconjugates in the field of science over the last decade, owing to their future prospect as a potential bioactive core, an update to this area is very much needed. The present review focusses on the synthesis, characterization and the various therapeutic applications of coumarin conjugates, i.e., sugar and nucleoside coumarin conjugates along with their perspective for future research.

Transporter-Mediated Drug Delivery

Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.

Late-Stage Functionalization through Click Chemistry Provides GLUT5-Targeting Glycoconjugate as a Potential PET Imaging Probe

The targeting of facilitative sugar transporters (GLUTs) has been utilized in the development of tools for diagnostics and therapy. The interest in this area is promoted by the phenomenon of alterations in cellular metabolic processes that are linked to multitudes of metabolic disorders and diseases. However, nonspecific targeting (e.g., glucose-transporting GLUTs) leads to a lack of disease detection efficiency. Among GLUTs, GLUT5 stands out as a prominent target for developing specific molecular tools due to its association with metabolic diseases, including cancer. This work reports a non-radiolabeled fluoride (19F) coumarin-based glycoconjugate of 2,5-anhydro-D-mannitol as a potential PET imaging probe that targets the GLUT5 transporter. Inherent fluorescent properties of the coumarin fluorophore allowed us to establish the probe's uptake efficiency and GLUT5-specificity in a GLUT5-positive breast cell line using fluorescence detection techniques. The click chemistry approach employed in the design of the probe enables late-stage functionalization, an essential requirement for obtaining the radiolabeled analog of the probe for future in vivo cancer imaging applications. The high affinity of the probe to GLUT5 allowed for the effective uptake in nutrition-rich media.

Gene variants of the SLC2A5 gene encoding GLUT5, the major fructose transporter, do not contribute to clinical presentation of acquired fructose malabsorption

Background

While role of ALDOB-related gene variants for hereditary fructose intolerance is well established, contribution of gene variants for acquired fructose malabsorption (e.g. SLC2A5, GLUT5) is not well understood.

Methods

Patients referred to fructose breath test were further selected to identify those having acquired fructose malabsorption. Molecular analysis of genomic DNA included (I) exclusion of 3 main ALDOB gene variants causing hereditary fructose intolerance and (II) sequencing analysis of SLC2A5 gene comprising complete coding region, at least 20 bp of adjacent intronic regions and 700 bp of proximal promoter.

Results

Among 494 patients, 35 individuals with acquired fructose malabsorption were identified based on pathological fructose-breath test and normal lactose-breath test. Thirty four of them (97%) had negative tissue anti-transglutaminase and/or deamidated gliadin antibodies in their medical records. Molecular analysis of SLC2A5 gene of all 35 subjects identified 5 frequent and 5 singular gene variants mostly in noncoding regions (promoter and intron). Allele frequencies of gene variants were similar to those reported in public databases strongly implying that none of them was associated with acquired fructose malabsorption.

Conclusions

Gene variants of coding exons, adjacent intronic regions and proximal promoter region of SLC2A5 gene are unlikely to contribute to genetic predisposition of acquired fructose malabsorption.

Positron Emission Tomography (PET) with 18F-FGA for Diagnosis of Myocardial Infarction in a Coronary Artery Ligation Model

Location and extent of necrosis are valuable information in the management of myocardial infarction (MI). Methods. We investigated 2-deoxy-2-18F-fluoro glucaric acid (FGA), a novel infarct-avid agent, for positron emission tomography (PET) of MI. We synthesized FGA from commercially available 18F-fluoro-2-deoxy-2-D-glucose (FDG). MI was induced in mice by permanently occluding the left anterior descending coronary artery. Biodistribution of FGA was assessed 1 h after FGA injection (11 MBq). PET/CT was conducted 1 h, 6 h, 1 d, 3 d, and 4 d after MI. Subcellular compartment of FGA accumulation in necrosis was studied by tracing the uptake of biotin-labeled glucaric acid with streptavidin-HRP in H2O2-treated H9c2 cardiomyoblasts. Streptavidin-reactive protein bands were identified by LC-MS/MS. Results. We obtained a quantitative yield of FGA from FDG within 7 min ( $\text{radiochemical}\text{purity}>99\%$ ). Cardiac uptake of FGA was significantly higher in MI mice than that in control mice. Imaging after 1 h of FGA injection delineated MI for 3 days after MI induction, with negligible background signal from surrounding tissues. Myocardial injury was verified by tetrazolium staining and plasma troponin (47.63 pg/mL control versus 311.77 pg/mL MI). In necrotic H9c2 myoblasts, biotinylated glucaric acid accumulated in nuclear fraction. LC-MS/MS primarily identified fibronectin in necrotic cells as a putative high fidelity target of glucaric acid. Conclusion. FGA/PET detects infarct early after onset of MI and FGA accumulation in infarct persists for 3 days. Its retention in necrotic cells appears to be a result of interaction with fibronectin that is known to accumulate in injured cardiac tissue.

Targeting of GLUT5 for Transporter-Mediated Drug-Delivery Is Contingent upon Substrate Hydrophilicity

Specific link between high fructose uptake and cancer development and progression highlighted fructose transporters as potential means to achieve GLUT-mediated discrimination between normal and cancer cells. The gained expression of fructose-specific transporter GLUT5 in various cancers offers a possibility for developing cancer-specific imaging and bioactive agents. Herein, we explore the feasibility of delivering a bioactive agent through cancer-relevant fructose-specific transporter GLUT5. We employed specific targeting of GLUT5 by 2,5-anhydro-D-mannitol and investigated several drug conjugates for their ability to induce cancer-specific cytotoxicity. The proof-of-concept analysis was carried out for conjugates of chlorambucil (CLB) in GLUT5-positive breast cancer cells and normal breast cells. The cytotoxicity of conjugates was assessed over 24 h and 48 h, and significant dependence between cancer-selectivity and conjugate size was observed. The differences were found to relate to the loss of GLUT5-mediated uptake upon increased conjugate size and hydrophobicity. The findings provide information on the substrate tolerance of GLUT5 and highlight the importance of maintaining appropriate hydrophilicity for GLUT-mediated delivery.

A comprehensive overview of substrate specificity of glycoside hydrolases and transporters in the small intestine : "A gut feeling"

The human body is able to process and transport a complex variety of carbohydrates, unlocking their nutritional value as energy source or as important building block. The endogenous glycosyl hydrolases (glycosidases) and glycosyl transporter proteins located in the enterocytes of the small intestine play a crucial role in this process and digest and/or transport nutritional sugars based on their structural features. It is for these reasons that glycosidases and glycosyl transporters are interesting therapeutic targets to combat sugar related diseases (such as diabetes) or to improve drug delivery. In this review we provide a detailed overview focused on the molecular structure of the substrates involved as a solid base to start from and to fuel research in the area of therapeutics and diagnostics.

Biosensor of Inflammation Biomarkers Based on Electrical Bioimpedance Analysis on Immobilized DNA Without Chemical Modification

The development of biosensors to identify molecular markers or specific genes is fundamental for the implementation of new techniques that allow the detection of specific Deoxyribonucleic acid (DNA) sequences in a fast, economic and simple way. Different detection techniques have been proposed in the development of biosensors. Electrical Bioimpedance Spectroscopy (EBiS) has been used for diagnosis and monitoring of human pathologies, and is recognized as a safe, fast, reusable, easy and inexpensive technique. This study proves the development of a complementary DNA (cDNA) biosensor based on measurements of EBiS and DNA's immobilization with no chemical modifications. The evaluation of its potential utility in the detection of the gene expression of three inflammation characteristic biomarkers (NLRP3, IL-1β and Caspase 1) is presented. The obtained results demonstrate that EBiS can be used to identify different gene expression patterns, measurements that were validated by Quantitative Polymerase Chain Reaction (qPCR). These results indicate the technical feasibility for a biosensor of specific genes through bioimpedance measurements on the immobilization of cDNA.

Insights into Substrate and Inhibitor Selectivity among Human GLUT Transporters through Comparative Modeling and Molecular Docking

The solute carrier 2 family is composed of 14 transporters, which are members of the major facilitator superfamily. Despite their high physiological importance, there are still many open questions concerning their function and specificity, and in some cases, their physiological substrate is still unknown. To understand the determinants of the substrate and inhibitor specificity, we modeled all human glucose transport carriers (GLUTs) and simulated their interaction with known ligands. Comparative modeling was performed with the @TOME-2 pipeline, employing multiple templates and providing an ensemble of models for each GLUT. We analyzed models in both outward-occluded and inward-open conformations, to compare exofacial and endofacial binding sites throughout the family and understand differences in susceptibility of GLUTs to the inhibitor cytochalasin B. Finally, we employed molecular docking and bioinformatics to identify residues likely critical for recognition of myo-inositol by GLUT13 and urate by GLUT9. These results provide insights into the molecular basis for the specificity for these substrates. In addition, we suggested a potential recognition site of glucosamine by GLUT11 to be evaluated in future experiments.

Integrating molecular probes and molecular dynamics to reveal binding modes of GLUT5 activatory and inhibitory ligands

Fructose transporter GLUT5 is characterized by unusual substrate specificity and is linked to a variety of metabolic disorders.